Geert Kleinnibbelink

Chapter 11 224 SUMMARY The general aim of this thesis was to investigate the acute and chronic effects of load challenges, either induced by pathological (e.g. PH) or physiological stimuli (e.g., exercise), on RV structure, function and mechanics. For this purpose, we performed exercise-related studies in healthy individuals and elite athletes ( Part 1: Chapters 2 – 5 ) and performed a series of studies in patients with PH ( Part 2: Chapters 6 – 9 ) using novel echocardiographic techniques (e.g., speckle tracking echocardiography and the strain-area loop). In Chapter 1 , we provided a general introduction on the background and rationale of this thesis. We provided an overview of the history of the cardiovascular system, followed by a discussion of the anatomical and functional differences between the RV and LV. Furthermore, we introduced novel echocardiographic techniques (i.e. speckle tracking echocardiography and strain-area loop) used in this thesis and provided an outline of this thesis. Part l – Right ventricular responses to acute and chronic exercise In Chapter 2 , we compared the impact of a single bout of high-intensity exercise under hypoxia versus normoxia on EICF on the RV and LV in healthy individuals.We demonstrated that a bout of 45-minute high-intensity exercise induced a reduction in functional indices of right- and left-sided cardiac function and mechanics. We found no impact of hypoxia on exercise-induced reduction in right- or left-sided cardiac function and mechanics. An additional, but equally important, finding was that the reduction in right- and left- sided cardiac function was present when echocardiography was performed during a standardized low-to-moderate-intensity recumbent exercise challenge, but not when examined under resting conditions. Taken together, these data indicate that EICF after short-term high-intensity exercise is not exaggerated under hypoxia, suggesting that an additional cardiac load (induced by hypoxia) on the RV does not necessarily relate to an exaggerated EICF in this setting. In Chapter 3 , we aimed to relate pre-training changes in cardiac function during acute hypoxic exercise to subsequent adaptations to a 12-week hypoxic endurance exercise training program on RV cardiac structure, function and mechanics in healthy individuals. First, we showed that hypoxic exercise training increased RV size, including diameter and area. Whereas measures of RV function remained largely unchanged, exercise training